The value of ΔH° for the formation of phosphorous trichloride from its constituent elements, P₂ (g) + 3Cl₂ (g) → 2PCl₃(g)
Is ________ kJ/mol

Question

The value of ΔH° for the formation of phosphorous trichloride from its constituent elements, P₂ (g)+ 3Cl₂ (g)→ 2PCl₃(g) Is ________ kJ/mol

Quizplus · Accepted Answer

To calculate ΔH° for the reaction, we need to subtract the sum of the enthalpies of formation of the reactants from the sum of the enthalpies of formation of the products.

The enthalpy of formation of a substance is the change in enthalpy when one mole of the substance is formed from its elements in their stable states at a given pressure and temperature (usually 25°C and 1 atm).

Using the enthalpies of formation from standard tables, we have:

ΔH° (reaction) = [2ΔH°f(PCl3) - ΔH°f(P) - ΔH°f(S) + 3ΔH°f(Cl2)] - [ΔH°f(PS) + 3ΔH°f(Cl2)]

ΔH° (reaction) = [2*(-319.6 kJ/mol) - 0 kJ/mol - 0 kJ/mol + 3*0 kJ/mol] - [17.6 kJ/mol + 3*0 kJ/mol]

ΔH° (reaction) = -720.5 kJ/mol

Therefore, the answer is C, -720.5 kJ/mol.

The Value of ΔH° for the Formation of Phosphorous Trichloride